Various electro-optical systems have been developed and used for reading optical indicia, such as barcodes. A barcode is a coded pattern of graphical indicia comprised of a series of bars and spaces of varying widths, the bars and spaces having differing light reflecting characteristics. The pattern of the bars and spaces encode information. Barcode may be one-dimensional (e.g., UPC barcode) or two-dimensional (e.g., DataMatrix barcode). Systems that read, that is, image and decode barcodes employing imaging camera systems arc typically referred to as imaging-based barcode readers.
Imaging-based barcode readers may be portable or stationary. A portable barcode reader is one that is adapted to be held in a user's hand and moved with respect to target indicia, such as a target barcode, to be read, that is, imaged and decoded. Stationary barcode readers are typically mounted in a fixed position, for example, relative to a point-of-sales counter often referred to as a bi-optic scanner (based on multiple windows and/or cameras), a slot scanner, or a single window stationary scanner.
Target objects, e.g., a product package that includes a target barcode, are moved or swiped past one of the one or more transparent windows and thereby pass within a field-of-view (“FOV”) of the stationary barcode readers. The barcode reader typically provides an audible and/or visual signal to indicate the target barcode has been successfully imaged and decoded. Sometimes barcodes are “presented”, as opposed to “swiped”. This typically happens when the swiped barcode failed to scan, so the operator tries a second time to scan it.
A typical example where a stationary imaging-based barcode reader would be utilized includes a point of sale counter/cash register where customers pay for their purchases. The stationary imaging-based barcode reader is typically enclosed in a housing that is installed in the counter and normally includes a vertically oriented transparent window and/or a horizontally oriented transparent window, either of which may be used for reading the target barcode affixed to the target object, i.e., the product or product packaging for the product having the target barcode imprinted or affixed to it. The sales person (or customer in the case of self-service check out) sequentially presents each target object's barcode either to the vertically oriented window or the horizontally oriented window, whichever is more convenient given the specific size and shape of the target object and the position of the barcode on the target object.
Both the stationary and portable imaging-based barcode readers can be equipped with a plurality of imaging cameras that will be referred to herein as a multi-camera, imaging-based scanner, barcode reader, or multi-imager scanner. In a multi-imager scanner, each camera system typically is positioned behind one of the plurality of transparent windows such that it has a different field-of-view from every other camera system. While the fields-of-view may overlap to some degree, the effective or total field-of-view (“TFV”) of the multi-imaging scanner is increased by adding additional camera systems. Hence, there is a greater desirability of multi-camera readers as compared to signal camera readers, which have a smaller effective field-of-view and require presentation of a target barcode to the reader in a very limited orientation to obtain a successful, decodable image, that is, an image of the target barcode that is decodable.
The camera systems of a multi-imaging scanner may be positioned within the housing and with respect to the transparent windows such that when a target object is presented to the housing for reading the target barcode on the target object, the target object is imaged by the plurality of imaging camera systems, each camera providing a different image of the target object. One example of such a system is found in U.S. patent application Ser. No. 11/862,568 filed Sep. 27, 2007 entitled MULTIPLE CAMERA IMAGING BASED BAR CODE READER that is assigned to the assignee of the present invention and is incorporated herein by reference.